Plant growth-promoting bacteria enhance tomato tolerance against tomato spotted wilt virus by unveiling optimal auxin levels.

Plant Growth-Promoting bacteria (PGPBs) provide a promising eco-friendly approach to enhancing plant resilience against viral infections. This study investigates the role of PGPBs in helping tomato cope with Tomato Spotted Wilt Virus (TSWV). Using compost made from tomato residues, we isolated and screened 42 bacterial strains for their PGP traits and adaptability to adverse environments. 7 bacterial strains exhibiting the highest scores of beneficial activities, including auxin and siderophore production, phosphate solubilization, and growth across extreme pH conditions (4-10), were selected for molecular identification and phylogenetic analysis. The potential of soils amended with each of the 7 PGPBs strains to enhance the growth of tomato was evaluated in genotypes classified as index 2 (tolerant) and index 4 (sensitive) on the pathogen index scale. Only Bacillus velezensis (PV123848.1), Dyella sp. (PP814986.1), and Bacillus licheniformis (PP814985) enable plants to withstand TSWV, shifting the tolerant genotype to index 1 and the sensitive one to index 2. Viral accumulation assessed by RT-qPCR confirmed this biological indexing in the presence of the three PGPBs. Alongside improving morphological parameters under TSWV challenge, PGPBs are likely to increase host auxin levels, thereby counteracting the virus's manipulation of this hormone during the tomato-TSWV interaction and limiting its spread. Our findings contribute to the theoretical framework for understanding the interaction between TSWV and tomato plants, providing new insights for future prevention and control of this disease. Moreover, we emphasize the disease-suppressing potential of PGPBs derived from agro-waste compost as a strategy for managing plant viral diseases.